The term "pressed bodies" in the following description refers to filling-containing masses which are processed without tension into structural elements by compression, injection molding, and extrusion. Typical graphite pressed bodies are, for example, carbon commutators. For fastening of commutator lamella on the rotor of an electric motor, the carbon commutator is, for example, soldered to a metallic carrier. For that purpose, the carbon commutators are often provided with a solderable adhered metallic layer or coating, by means of which the carbon commutator is soldered to the carrier. For improved adhesion of the solderable metallic layer, pre-treatment of the surface of the pressed body is necessary. The previously known methods for pre-treatment of carbon commutators are mechanical roughening methods, e.g., sandblasting methods.
U.S. Pat. No. 4,844,781, SANCHEZ et al., discloses a method of surface treating carbon fibers in a substantially water-free solution of an amine compound in a bipolar solvent, preferably an aprotic bipolar solvent such as acetonitrile, dimethyl-formamide or dimethylsulfoxide ("DMSO"). This treatment leads to oxidation of the carbon fibers, which improves bonding between the fibers and an embedding matrix of synthetic resin. This bonding is a function of chemical processes which need not be detailed here.